Currently, many applications based on DB exist and DBMS that performs a set of processing and management related to DB is extremely important. One feature of DB is that an enormous amount of data is handled. Thus, in many computer systems in which DBMS operates, a system configuration in which a storage apparatus having large-capacity disks is coupled to a computer in which DBMS operates and DB data is stored in the storage apparatus is common.
When this system configuration is adopted, data is stored on disks of the storage apparatus and access to disks is certain to occur when processing on DB (DB processing) is performed. Particularly in super large-scale DB of petabyte class, an enormously long time is needed for processing to search for specific data from data of the DB. As a technology to accelerate search processing to search for specific data from a large amount of data, the technology disclosed in PTL 1 is known.
The technology disclosed in PTL 1 is a technology to multiplex reading of data by dynamically creating a task each time data is read and performing tasks in parallel in a non-ordered sequence. According to DBMS using the technology, when compared with conventional DBMS that performs tasks in the order of creation, search performance can dramatically be improved.